"The city of San Siroco is sinking. The basement of Dr. Tamsin Rivers, the arrogant, selfish head of the research team assigned to find the source of the subsidence, is sinking faster. As Tamsin grows obsessed with the distorting dimensions of the room at the bottom of the stairs, she finds a door that didn't exist before - and one night, it opens to reveal an exact physical copy of her. This doppelgänger is sweet and biddable where Tamsin is calculating...

"Andy and Terry live in a 169-story treehouse. (It used to be a 156-story treehouse, but they've added 13 more stories.) It now has a kangaroo-riding range, a whatever-weather-you-want dome and a hall of funhouse mirrors--the perfect place to hide from the truancy officer who is trying to catch them and make them go to school! Unfortunately, the hall of funhouse mirrors is also the place where their evil trouble-making twins, Anti-Andy, Terrible Terry...

Haunted by trauma from her past and compounded by a string of eerie coincidences, Adelaide grows increasingly certain that something bad is going to befall her family. After spending a tense beach day with their friends, Adelaide and her family return to their vacation home. When darkness falls, the Wilsons discover the silhouette of four figures holding hands as they stand in the driveway: doppelgangers of themselves.

Beth has never had any friends and she has always been kind of invisible at school, so when a new girl, Lizzie, moves into her building she thinks that she has finally found a best friend; but things turn creepy when Lizzie starts copying Beth so exactly that she might be a twin--and Beth starts to wonder if Lizzie is a friend or something a lot more sinister.